1. Technical Field of the Invention
This invention relates to foams containing amide groups prepared from organic polyisocyanates and polyfunctional organic acids. More particularly, this invention relates to the preparation of foamed reaction products that contain amide groups, the foamed reaction products being prepared by reacting an organic polyisocyanate with an addition reaction product of a polyoxyalkylene reactant with an organic polycarboxylic acid reactant; such addition reaction product containing terminal carboxylic acid groups and being referred to herein as a polyoxyalkylene derivative of an organic polycarboxylic acid containing terminal carboxylic acid groups.
2. Prior Art
It is known to prepare polyurethane foams by the reaction of an organic polyisocyanate with a polyoxypropylene polyol using an extraneous blowing agent such as a fluorinated hydrocarbon. However, fluorinated hydrocarbons create environmental problems when released to the atmosphere.
It is known to prepare polyurethane foam using carbon dioxide generated by the reaction of an organic polyisocyanate with water. The disadvantage here is that fluorinated hydrocarbon blowing agents are needed to make most polyurethane foams.
The preparation of polyurethane foam and the general background relating to the reaction of acids and isocyanates is discussed in the well-known text by Saunders and Frisch, "Polyurethanes Chemistry and Technology in High Performance Polymers", Interscience: New York, 1962; Vol. XVI, Part I.
Lichtenberg also describes the use of water and formic acid as blowing agents in preparing polyurethane foam (Lichtenberg, F. W., Ed. "CFC's and the Polyurethane Industry"; SPI, Vol. 2).
U.S. Pat. No. 4,868,277 is directed toward making nonelastomeric thermoplastic polyesteramides. Important differences between U.S. Pat. No. 4,868,277 and the present invention are primarily the materials described in U.S. Pat. No. 4,868,277 are not foams. The acids used to cap the polymer diols in U.S. Pat. No. 4,868,277 have from 6 to 14 carbons. Difunctional isocyanates and acids provide linear polymers in U.S. Pat. No. 4,868,277, hence their thermoplastic nature. The carboxyl terminated polymers employed in U.S. Pat. No. 4,868,277 are derived from dicarboxylic acids and polymeric diols. Materials with a higher functionality than 2 are not used. A large molar amount of short chain diacid as compared with the carboxyl terminated prepolymer in 4,868,277 as well (&gt;10:1). A solvent is used which is not possible in the present invention unless it would also serve as an auxiliary blowing agent and would not be used per se as a solvent for the reaction medium.
EP 194,058 is directed to catalyzing the reaction of polycarboxylic acids and diisocyanates by using alkali metal salts (basic salts) in solvent consisting of N,N'-dimethyl alkylene urea alone or with cosolvent. This method is inherently not useful for making foams because of the solvent; the carbon dioxide evolved escapes and is not used to form bubbles. The suggested uses appear to preclude foams. The use of carboxylate terminated polyether esters or amides is not suggested (as the carboxylic acid component). All examples are directed to formation of aromatic polyamides.